The attack of an army ant

Student Samantha Hodgson studies at the University of Gloucestershire, and is writing about the swarm raiding technique of army ants ahead of our 24 hour lecture on ants and bees, hosted by Professor Adam Hart.

Army ants are unparalleled in the animal world when it comes to raid strategy. They are capable of capturing tens of thousands of prey in a single day using a terrifying swarm tactic to cover the largest area possible.

Eciton burchellii, found in the neotropical forests of central and South America, is a nomadic species with no fixed nest. Instead, the enormous colonies; often over 500,000 strong, travel to a different location every night.

Raid parties are released from the colony to gather food. As many as 200,000 individuals are involved in the war-like ‘swarm raids’ used to capture their prey. The foraging troops branch out and spread to cover an area up to 20 metres wide. An ant tsunami follows, taking out everything in its path. Army ants will use their own bodies to fill holes in the ground, smoothing out the path for following ants, allowing the onslaught to be as effective as possible.

Eciton burchelliiprey on arthropods including other ant species, but will kill other animals that don’t flee the area as they approach. Small reptiles and frogs can all become casualties of army ant raids.

Their brutal assault strategy is not the only interesting aspect of these tiny warriors’ lives. They have developed an innovative technique to counteract their lack of a fixed nest site. Instead of a typical underground ant nest they create temporary nests from their interlinking bodies, using hooks on the ends of their feet. The cylindrical ‘bivouac’ formed protects the lone queen and her larvae. This tactic enables the colony to continue travelling to new areas without putting the queen at risk.

The only time the colony will remain stationary is during a 20 day period in the colonies cycle when the queen lays her eggs. During this time the bivouac will not disperse however the raids are still sent out every other day.